[PATCH 03/11] repo-settings: pack.useSparse=true

["Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com>]

From: Derrick Stolee <dstolee@microsoft.com>

If a repo is large, then it probably has a very large working
directory. In this case, a typical developer's edits usually impact
many fewer paths than the full path set. The sparse treewalk
algorithm is optimized for this case, speeding up 'git push' calls.

Use pack.useSparse=true when core.size=large.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 Documentation/config/core.txt | 4 ++++
 Documentation/config/pack.txt | 3 ++-
 builtin/pack-objects.c        | 9 +++++----
 repo-settings.c               | 6 ++++++
 repo-settings.h               | 1 +
 5 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/Documentation/config/core.txt b/Documentation/config/core.txt
index ea64f675fa..df357f5af5 100644
--- a/Documentation/config/core.txt
+++ b/Documentation/config/core.txt
@@ -616,3 +616,7 @@ core.size::
 +
 * `index.version=4` uses prefix-compression to reduce the size of the
 .git/index file.
++
+* `pack.useSparse=true` uses the sparse tree-walk algorithm, which is
+optimized for enumerating objects during linkgit:git-push[1] from a
+client machine.
diff --git a/Documentation/config/pack.txt b/Documentation/config/pack.txt
index 9cdcfa7324..e6f44de104 100644
--- a/Documentation/config/pack.txt
+++ b/Documentation/config/pack.txt
@@ -112,7 +112,8 @@ pack.useSparse::
 	objects. This can have significant performance benefits when
 	computing a pack to send a small change. However, it is possible
 	that extra objects are added to the pack-file if the included
-	commits contain certain types of direct renames.
+	commits contain certain types of direct renames. Defaults to
+	false, unless `core.size=large`.
 
 pack.writeBitmaps (deprecated)::
 	This is a deprecated synonym for `repack.writeBitmaps`.
diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
index 41d7fc5983..f26b3f2892 100644
--- a/builtin/pack-objects.c
+++ b/builtin/pack-objects.c
@@ -34,6 +34,7 @@
 #include "dir.h"
 #include "midx.h"
 #include "trace2.h"
+#include "repo-settings.h"
 
 #define IN_PACK(obj) oe_in_pack(&to_pack, obj)
 #define SIZE(obj) oe_size(&to_pack, obj)
@@ -2707,10 +2708,6 @@ static int git_pack_config(const char *k, const char *v, void *cb)
 		use_bitmap_index_default = git_config_bool(k, v);
 		return 0;
 	}
-	if (!strcmp(k, "pack.usesparse")) {
-		sparse = git_config_bool(k, v);
-		return 0;
-	}
 	if (!strcmp(k, "pack.threads")) {
 		delta_search_threads = git_config_int(k, v);
 		if (delta_search_threads < 0)
@@ -3330,6 +3327,10 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix)
 	read_replace_refs = 0;
 
 	sparse = git_env_bool("GIT_TEST_PACK_SPARSE", 0);
+	prepare_repo_settings(the_repository);
+	if (!sparse && the_repository->settings->pack_use_sparse != -1)
+		sparse = the_repository->settings->pack_use_sparse;
+
 	reset_pack_idx_option(&pack_idx_opts);
 	git_config(git_pack_config, NULL);
 
diff --git a/repo-settings.c b/repo-settings.c
index 7e6e65d60c..026ab9c1a0 100644
--- a/repo-settings.c
+++ b/repo-settings.c
@@ -14,6 +14,7 @@ static int git_repo_config(const char *key, const char *value, void *cb)
 		if (!strcmp(value, "large")) {
 			UPDATE_DEFAULT(rs->core_commit_graph, 1);
 			UPDATE_DEFAULT(rs->gc_write_commit_graph, 1);
+			UPDATE_DEFAULT(rs->pack_use_sparse, 1);
 			UPDATE_DEFAULT(rs->index_version, 4);
 		}
 		return 0;
@@ -26,6 +27,10 @@ static int git_repo_config(const char *key, const char *value, void *cb)
 		rs->gc_write_commit_graph = git_config_bool(key, value);
 		return 0;
 	}
+	if (!strcmp(key, "pack.usesparse")) {
+		rs->pack_use_sparse = git_config_bool(key, value);
+		return 0;
+	}
 	if (!strcmp(key, "index.version")) {
 		rs->index_version = git_config_int(key, value);
 		return 0;
@@ -44,6 +49,7 @@ void prepare_repo_settings(struct repository *r)
 	/* Defaults */
 	r->settings->core_commit_graph = -1;
 	r->settings->gc_write_commit_graph = -1;
+	r->settings->pack_use_sparse = -1;
 	r->settings->index_version = -1;
 
 	repo_config(r, git_repo_config, r->settings);
diff --git a/repo-settings.h b/repo-settings.h
index 9b8104042e..b50228f992 100644
--- a/repo-settings.h
+++ b/repo-settings.h
@@ -4,6 +4,7 @@
 struct repo_settings {
 	char core_commit_graph;
 	char gc_write_commit_graph;
+	char pack_use_sparse;
 	int index_version;
 };
 
-- 
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